It has long been desirable to provide efficient, simple and relatively inexpensive fluid to fluid heat exchangers. British Patent Specification No. 1,356,114, published June 12, 1974, discloses an impingement type exchanger in which a plurality of tubular nozzles direct hot and cold air perpendicularly against opposite sides of an intermediate heat exchanger wall. Opposed longitudinal air jets have been used to dry fabric webs, as disclosed in U.S. Pat. No. 3,827,639 to Belue et al., issued Aug. 6, 1974.